The Guggenheim Solar ETFtan retreated 3% to $17.83, while the Market-Vectors Solar Energy ETF lost 3% to $41.35.

Solar stocks had a heady start to the year, far outpacing the broader U.S. market. But those gains are waning as industry executives warn there still are too many solar panels in the market and no let-up in aggressive price pressure to win new business.

The Guggenheim Solar ETFtan retreated 3% to $17.83, while the Market-Vectors Solar Energy ETF lost 3% to $41.35.

Solar stocks had a heady start to the year, far outpacing the broader U.S. market. But those gains are waning as industry executives warn there still are too many solar panels in the market and no let-up in aggressive price pressure to win new business.